fixed index variable parsing 
Update lib/logstash/outputs/elasticsearch_river.rb
updated changelist for fix for LOGSTASH-819
Update CHANGELOG
Merge pull request #302 from paulczar/master

improve outputs / elasticsearch_river
-
- don't use "puts", use logger.debug (LOGSTASH-832)
Merge branch 'master' into aws-iam-roles
added old config options for backward compatibility with deprecation warnings & info